This invention pertains to the arts of high speed data and digital telephony interconnect, wiring, termination, and routing technologies, especially those technologies related to provision of redundant, switch-over, back-up or protection of critical interconnects.
None.
This invention was not developed in conjunction with any Federally-sponsored contract.
Not applicable.
High speed data and digital telelphony interconnection schemes are well-known within the art of data and telecommunications, including multi-megabit to gigabit-per-second data rates such as North American transmission standards including STS-1 electrical, STS-3 electrical, VT1.5 electrical, DS-1/T1, DS-3/T3, 25M asynchronous transfer mode (xe2x80x9cATMxe2x80x9d), asynchronous digital subscriber line (xe2x80x9cADSLxe2x80x9d), high-speed digital subscriber line (xe2x80x9cHDSLxe2x80x9d), and optical media such as OC-1, OC-3, OC-12, OC-48, OC-192, OC-768; international optical standard media such as synchronous digital hierarchy (xe2x80x9cSDHxe2x80x9d) STM-1, STM-4, STM-16, and STM-64; various standards from the European Telecommunications Standards Institute (xe2x80x9cETSIxe2x80x9d) and the International Telecommunications Union (xe2x80x9cITUxe2x80x9d) E1 and E3; Japanese standards including J1 and J2; and local area network (xe2x80x9cLANxe2x80x9d) interfaces and transmission protocols such as EtherNet, Fast EtherNet, Giga-bit EtherNet, and Token Ring.
Because of the transmission line characteristic and signal integrity considerations necessary to successfully route and interconnect signals of these frequencies, great care must be taken to avoid termination impedance mismatches, unnecessary stubs, and cross talk. Most cabling and connectors used in these installations are either twisted-pair and/or shielded designs.
Turning to FIG. 1, a simple block diagram of a communications system is shown. In this case, the system has a shelf comprising two or more cards (11 and 12) and a backplane (10) into which the cards are installed. In this example, the signal cabling interconnect is made via xe2x80x9cfront panelxe2x80x9d access, or on the side from which the cards are installed and removed. Signal cables are connected (13 and 14) to the cards (11 and 12) via signal connectors such as coaxial, twin-axial, tri-axial, twisted-pair or D-connectors.
If a card fails or otherwise needs to be replaced, it must be removed from the shelf from the front panel direction. This necessitates the disconnection of the signal cables, which requires the data or telecommunications traffic carried on those cables to be re-routed to other systems in order to avoid interruption of service. So, a technician or group of technicians would usually perform several system commands to re-route the traffic, disable the communications path, remove and replace the card, re-enable the communications path, and re-route the traffic to the new card.
In order to lessen the number of steps and time involved with this process, and increase the xe2x80x9cavailability timexe2x80x9d of these systems, some systems provide for backup or redundant cards in the shelf. Typically, the backup or xe2x80x9cprotectionxe2x80x9d card is idle until placed into service as the result of needing to remove an active card. While this solution is a viable approach for system interconnection schemes which involve routing and interconnect of the signals to the cards via the backplane, it is not easily realizable with front-panel access systems. In front-panel access systems, the failed or removed card must be disconnected from the signal cable at some point, which causes an interruption in the service. However, many telecommunications systems operators, such as telephone companies, Internet service providers, and large privately-owned switch rooms, prefer the front-panel access arrangement for maintenance and installation reasons. Further, many countries, especially throughout Europe, specify and require systems to be provided with front-panel access.
Some schemes of protection interconnect have employed a split or xe2x80x9cYxe2x80x9d connection to two terminators, as shown in FIG. 1. The primary terminator (11) line interface unit (xe2x80x9cLIUxe2x80x9d) and the protection terminator (12) LIU impedances must be adjusted accordingly such that the two terminations presented in parallel meet the impedance of the cable (15). But, as the primary terminator is removed from the interconnect to allow connection of the replacement card or circuit, only the protection terminator is present on the signal, which may cause severe signal distortion and a impedance mismatch. At higher frequencies, the disconnected and un-terminated portion of the xe2x80x9cYxe2x80x9d cable may also present undesirable stub characteristics.
This general mechanical and electrical representation can be applied to many systems, such as Private Branch Exchanges (xe2x80x9cPBXxe2x80x9d), data routers, Central Office switches, etc.
Therefore, there is a need in the art for a signal interconnection method and system which allows for the re-routing of a signal from a primary point of termination to a secondary point of termination, mechanical and electrical disconnection of the primary point of termination from the signal cable, mechanical and electrical connection of a replacement primary point of termination to the signal cable, and re-routing of the signal to the replacement point of termination. Further, there is a need in the art to maintain the termination impedance during all of these steps in order to maintain signal integrity. Finally, there is a need in the art for this system and method to allow continuous, uninterrupted service of the traffic carried on the signal cable.
The present invention is useful for data and telecommunications signals at all speeds and frequencies in the electrical domain, and also for signals in the optical domain, including STS-1 electrical, STS-3 electrical, VT1.5 electrical, DS-1/T1, DS-3/T3, 25M asynchronous transfer mode (xe2x80x9cATMxe2x80x9d), asynchronous digital subscriber line (xe2x80x9cADSLxe2x80x9d), high-speed digital subscriber line (xe2x80x9cHDSLxe2x80x9d), and optical media such as OC-1, OC-3, OC-12, OC-48, OC-192, OC-768; international optical standard media such as synchronous digital hierarchy (xe2x80x9cSDHxe2x80x9d) STM-1, STM-4, STM-16, and STM-64; various standards from the European Telecommunications Standards Institute (xe2x80x9cETSIxe2x80x9d) and the International Telecommunications Union (xe2x80x9cITUxe2x80x9d) E1 and E3; Japanese standards including J1 and J2; and local area network (xe2x80x9cLANxe2x80x9d) interfaces and transmission protocols such as EtherNet, Fast EtherNet, Giga-bit EtherNet, and Token Ring.
A primary interface card for receiving a signal is equipped with a bypass or shunting relay, the control of which is managed by a backup or protection interface card. The cable interconnect from far-end equipment to the primary interface card is provided with a make-before-break connector to the primary interface card, and a pig tail cable to the protection card. Upon command, the protection card may command the relay to shunt the signal from the far end equipment around the primary interface card to the protection card. Then, the cable is unplugged from the primary interface card, with the make-before-break connector providing a signal path from the far-end equipment to the protection card before continuity through the shunting relay is lost. The primary interface card can then be removed and replaced, and the process reversed to redirect traffic to the primary interface card. Thus, the primary interface card is electrically or optically isolated, mechanically removed and replaced, and electrically or optically reconnected allowing continuous, uninterrupted service of the signal and traffic by the protection card during the maintenance action.